1. Field of the Invention
The present invention relates to a paging apparatus equipped with a clock function to measure the time and display it.
2. Description of the Related Art
As a new type of a pager system, a system has recently been developed in which a base station transmits message information, and one of the paging apparatuses subscribed to this system displays the message information. A paging signal used in this system is exemplified in FIG. 8. As illustrated, one frame is time-divided into a plurality of groups each of which is further time-divided into a synchronization word and a plurality of calling words. In each calling word are inserted an identification (ID) code and a message code.
When calling a paging apparatus, a caller dials a telephone number assigned to the paging apparatus, thus reaching the base station, and transmits message information to the base station. Then the base station generates the ID code preassigned to the selected paging apparatus and the message code which is the message information encoded. The ID code and the message code are inserted into one of empty calling words in that one of multiple groups in one frame to which that paging apparatus belongs before transmission to the paging apparatus.
The paging apparatus may be designed as follows. The paging signal transmitted from the base station is received by a radio circuit through an antenna and demodulated by a demodulation circuit for subsequent application to a control circuit. The control circuit collates the ID code contained in the demodulated paging signal with the self-ID code previously stored in ID-ROM. When a coincidence occurs between the codes, the control circuit recognizes the generation of a call to the apparatus to produce a ringing signal. This ringing signal is applied via a driving circuit to a loudspeaker which is in turn generates a ringing tone, whereby the user is informed that a call has been made to him.
Upon the occurrence of a coincidence between the ID codes, the control circuit receives the message code received following the ID code. After being subjected to an error correcting process, the message code is decoded and the decoded message data is applied to a display driving circuit. Consequently the message is displayed on a liquid crystal display (LCD) by the display driving circuit. Therefore, the user can understand the message from the caller through the liquid crystal display at the time of generation of the call. The display message is erased from the liquid crystal display when the user depresses a stop switch.
Recently, a new type of a paging apparatus has been developed which is equipped with a clock function. This type of a paging apparatus has an integrated clock circuit. Information of time received by this integrated clock circuit during a call waiting period is displayed on a message display. Carrying around this type of a paging apparatus, therefore, the owner can use this apparatus as a clock, which is very convenient.
Conventional paging apparatuses of this type have a mode switch and first and second select switches in addition to a switch to instruct disabling generation of a ringing tone or message display and enabling message display. The mode switch serves to switch between the ordinary paging mode and a time setting mode. The first select switch serves to select a digit, such as hour or minute. The second select switch serves to select the value of the digit, "hour" or "minute," selected by the first select switch. Time setting is executed by combining these switches. The prior art design inevitably results in an increased number of switches, thus enlarging the paging apparatus. As a solution to this shortcoming, the switches may be designed compact, which will however deteriorate the operability.